A capacitive sensor is a sensor which can detect concavo-convex shapes or the like of a measuring object from the capacitance change between a pair of electrode layers disposed so as to face each other, with a dielectric layer interposed therebetween.
Generally, capacitance in a capacitive sensor is represented by the following Formula (1):C=ε0εrS/d  (1)
Here, C represents capacitance; ε0 represents the permittivity of free space; εr represents the relative permittivity of a dielectric layer; S represents the area of an electrode layer; and d represents the distance between electrodes.
Furthermore, Patent Literature 1 describes a capacitive sensor sheet including a dielectric layer formed from an elastomer; a top electrode layer and a bottom electrode layer that are formed on the top surface and the bottom surface of the dielectric layer, respectively. In this capacitive sensor sheet, since the dielectric layer is formed from an elastomer, the dielectric layer is capable of repeated elastic deformation. Furthermore, in regard to this capacitive sensor sheet, since the various electrode layers contain carbon nanotubes, the electrode layers can change their shapes in conformity with the deformation of the dielectric layer.
Therefore, the capacitive sensor sheet described in Patent Literature 1 can change its shape in conformity with the deformation or motion of a measuring object, even if the measuring object is flexible and has a high degree of elongation. Thus, the capacitance changes as a result of this deformation.